Claims
- 1. A method for fabricating a grid-controlled electron source comprising the steps of:
- forming a continuous sheet laminate by bonding a barrier layer and a metallic layer to opposite sides of a sheet of insulating material,
- removing separated areas of said laminate to form an array of holes extending through the entire thickness of said laminate, said holes being separated by web members consisting of the original thickness of said web members,
- bonding the barrier layer side of said web members to the emissive surface of a thermionic cathode, and said removing step being performed prior to said bonding of said laiminate to said emissive surface.
- 2. The method of claim 1 further comprising the step of making electrical contact, insulated from said cathode, to said metallic layer.
- 3. The method of claim 1 wherein said removing of said portions is by abrasion.
- 4. The method of claim 1 wherein the portion of said cathode adjacent said emissive surface is a porous metal body impregnated with an active salt composition.
- 5. The method of claim 4 wherein said porous metal body comprises sintered tungsten particles.
- 6. The method of claim 4 wherein said salt composition comprises barium and aluminum oxides.
- 7. The method of claim 1 wherein said insulating layer is boron nitride.
- 8. The method of claim 1 wherein said barrier layer is metallic.
- 9. The method of claim 1 wherein said metallic layer comprises at least one metal of the class consisting of zirconium and titanium.
- 10. The method of claim 1 wherein said step of attaching said barrier layer to said emissive surface comprises thermal bonding.
GOVERNMENT CONTRACT
The invention was reduced to practice under U.S. Army Electronics Command Contract No. DAAB07-75-C-1321.
The invention pertains to grid-controlled electron sources, such as used in high frequency tubes such as planar triodes and in electron guns for beam-type microwave tubes. For a triode to operate at extremely high frequencies, it is necessary that the control grid be located very close to the cathode, so that the transit time of electrons between cathode and grid is minimized. In other grid-controlled sources, such as guns for linear-beam microwave tubes, as well as many grid-controlled power tubes, it is desirable to have the maximum transconductance and the maximum amplification factor. These can be simultaneously achieved only by a fine-mesh control grid located very close to the cathode.
The improvement of grid-controlled electron sources by conventional techniques of supporting the grid spaced from the cathode has reached its highest development in planar triodes where parallel grid wires are placed in tension across a frame which is then carefully spaced a few mils from the flat cathode surface. The limitations of this conventional structure posed by mechanical and thermal distortion of the parts and by vibration of the grid have led to attempts to mount the grid elements firmly on the cathode with intervening, insulating support members. In these previous attempts a network of insulating material was deposited on the cathode surface, as by chemical vapor deposition. Metal conductors were then deposited on the top surface of the insulator to form the control electrode. These previous attempts to fabricate bonded control grids were not successful because in the deposition processes the emissive cathode invariably became poisoned.
An object of the invention is to provide a grid-controlled electron source in which the control elements are mounted directly on the emissive cathode with insulative supports therebetween.
A further objective is to provide a control grid which is very close to the cathode and which has very small openings between control elements. A further object is to provide a process for fabricating a grid-controlled electron source by bonding the control elements directly to the cathode via insulating supports.
The above objects are achieved by fabricating the grid structure as a laminated sheet of insulating material with metal layers bonded to both opposite surfaces. The laminated sheet forms web members with openings therebetween. One of the metal layers is attached to the emissive cathode. The other, insulated metal layer forms the control electrode. In a preferred embodiment, the laminated sheet is formed as a continuous sheet and then portions are removed, as by abrasion, to form the openings between web members. The web structure is then attached to the emissive cathode surface. The lower metal layer may be bonded firmly to the cathode surface, as by thermal diffusion.
US Referenced Citations (5)
Foreign Referenced Citations (2)
| Number |
Date |
Country |
| 1,232,272 |
Jan 1967 |
DT |
| 275,238 |
Jul 1969 |
SU |
Patent Grant
4096406
